Facebook has several features requesting users to add not only their username but passwords to other websites, to add friends. The same can not be said of Facebook [0]. The CEO is allegedly said to take advantage of journalists who provided their details to access journalists' private emails [1].

[0] http://www.wired.com/epicenter/2010/11/google-facebook-data/

[1] http://www.businessinsider.com/how-mark-zuckerberg-hacked-in...